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to measure. Disadvantage of this method is the slide contact, the credibility is bad, the
interference is big, need usually to replace and maintain it. This other is through non-
contact temperature sensor to measure (such as infrared, then color etc.) But this
method can not use to measure the temperature of closed system, and the accuracy is
low, the anti-interference ability is bad, the cost is big, the application is restricted. In
order to overcome above disadvantage, has designed a wireless temperature measur-
ing device. Install it on rotating seed rod; through transceiver transmit the measure
data to display. Solve measure device power-supply and anti-interference problem.
This designs low cost, easy to use and reliable. It has obvious advantage and good
promotion value in the particular situation of the inconvenient wiring.
2 The Hardware Design of Temperature Measuring Devices
2.1 The Design of Temperature Measuring Transmitting Circuit
Fig. 1 is the hardware structure chart of measuring device Installed on a rotating seed
rod; it is composed of Micro Control Unit (MCU), the wireless transmitter, the ther-
mocouple and peripheral circuit. In this design chooses 51 series MCU and PT2262
wireless transmitter.
As the seed crystal in the high-temperature furnace and rotating state, and the
growth process longer (about 21 days). In order to solve the problem of the electric
circuit power supply, make use of hand dynamo principle, has designed a set of gen-
erating electricity device, and installed it on the seed rod. Make use of the seed rod
rotation to generate electricity, charge the storage battery. Ensure temperature meas-
ure device to use electricity power for a long time.
For economizing energy, MCU works at the sleep or work state. The time ratio of
two states can be set through the DIP switch of measure meter. Before MCU enters a
sleep state, it turns off all peripheral power to economize system power supply. When
MCU is asleep it can be awaked by timer interrupt into work state. Complete tempera-
ture measurement and send out measurement data to receiver.
After transmitter is initialized, MCU turn on the peripheral device power switch.
Thermocouple signal processing by amplification is send to ICL7135. The ICL7135 is
four and a half bits AD converter. Its advantage is high-accuracy, low-price, anti-
interference ability strong, converting rate moderate etc. The data processing as fol-
lows: first, MCU reads a converting value of ICL7135, and return to the voltage value
(mV) of the thermocouple, and use Κ degree to process it linearly, gets at present
temperature measured CT(n), gets CT value with CT=[CT(n)+CT(n-1)]/2 linear filter.
Suppose that the cold end's temperature is CL at present, then actual temperature is
CN=CT+CL, and through PT2262 and 315MHz transmit a Cn value and completes a
transmitting process. Last MCU turns off peripheral power. Return to sleep state.
When sleep time arrive after, MCU turn on peripheral power switch, repeat above
process.
2.2 The Design of Temperature Measuring Device Receiving Circuit
Receiving circuit hardware structure is shown Fig. 2.
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